Cancer mortality in a radiation-exposed cohort of Massachusetts tuberculosis patients.

The mortality experience of 13,385 tuberculosis patients treated between 1925 and 1954 in Massachusetts was determined through August 1986. Among 6,285 patients examined by X-ray fluoroscopy an average of 77 times during lung collapse therapy and followed for up to 50 yr (average = 25 yr), no increase in the total number of cancer deaths occurred [standardized mortality ratio (SMR) = 1.05, n = 424]. In contrast, the 7,100 patients treated by other means were at significant risk of dying from cancer (SMR = 1.3), especially of sites linked to cigarette smoking and alcohol use. Among the irradiated patients, estimates of mean radiation doses to the breast, lung, esophagus, and active bone marrow were 0.75, 0.84, 0.80, and 0.09 Gy, respectively. Cancers of the breast (SMR = 1.4, n = 62) and esophagus (SMR = 2.1, n = 14) were significantly increased. The risk of esophageal cancer, however, decreased with time since exposure. Lung cancer (SMR = 0.8, n = 69) and leukemia (SMR = 1.2, n = 17) were not elevated. Despite a wide range of doses to the lung, reaching over 8 Gy, there was no evidence of a dose response. Lung cancer risk also did not vary by time since exposure or age at exposure. Adjustment for smoking and the amount of lung tissue at risk did not appreciably modify these findings. These data suggest that frequent exposures to low doses of radiation over a period of several years increase the occurrence of cancer of the breast. When compared with studies of atomic bomb survivors, however, the fractionated exposures experienced by this cohort appear less effective in causing lung cancer than single exposures of the same total dose.

Breast cancer after multiple chest fluoroscopies: second follow-up of Massachusetts women with tuberculosis.

A second follow-up was conducted of 1742 women with tuberculosis who were treated in one of two sanatoria in Massachusetts between 1930 and 1956. One hospital treated only children under the age of 17. Patient follow-up was extended from 1975 through 1980, and an additional 18 breast cancers were identified from hospital records, death certificates, and responses to a mailed questionnaire. Vital status was established for 97% of the subjects. Among 1044 women who were examined an average of 101 times with X-ray fluoroscopies during lung collapse therapy, 55 breast cancers were observed in contrast to 35.8 expected, based on incidence rates from the general population. No excess was found for 698 women treated by other means (19 observed versus 22.8 expected). Excess breast cancer risk did not appear until 15 years after initial exposure and was present at the end of 50 years of observation. Risk appeared to decrease with increasing age at exposure. Estimates of radiation dose to the breast for individuals (mean = 96 rad) were based on the most current information for the numbers of fluoroscopies, reconstruction of exposure conditions, and absorbed dose calculations. The relation between dose and breast cancer risk was consistent with linearity up to 400 rads (4 Gy). For 10-year survivors, the absolute excess risk was 5.5/1 million woman-year-rad, the excess relative risk per rad was 0.73%, and the relative risk at 100 rad was 1.7. These data indicate that a woman's lifetime risk of breast cancer is influenced by events occurring in early reproductive life, that low-dose fractionated exposures are as effective as single exposures of the same total dose in inducing breast cancer, and that risk of radiogenic breast cancer persists for many years, and perhaps for life.

Twin study of multiple sclerosis: an epidemiologic inquiry.

The National Research Council Twin Registry comprises 16,000 pairs of white male twins, both members of which had been in military service, mainly in World War II. All their available military and Veterans Administration records and their responses to a 1965 to 1970 NRC questionnaire have been coded as to disease. Upon review we found 16 cases of multiple sclerosis (MS) among 15 pairs of twins, for an age-specific prevalence rate of 51 per 100,000 veterans aged 43 to 53--about half the expected frequency. Of the 15 sets, three sets refused cooperation and three were unavailable for study. Nine sets were examined and interviewed together with the mother. One of five monozygotic twin pairs was concordant for MS and in another the co-twin of an MS case had had a solitary episode of retrobulbar neuritis; all others were discordant. There were more definable environmental events (as noted below) among the affected twins than among the unaffected co-twins. The greatest excess was within the 20 years before onset. Summing events across the four 5-year periods before onset, among the 10 MS versus the eight not-MS individuals, there were 5:1 instances of trauma, 8:2 or operation, 7:1 of ether anesthesia, 7:1 of allergy, 10:5 of infection, and 9:0 of animal exposure. Summing these same events within each 5-year period, the MS:control ratios were 9:1, 10:2, 12:3, and 15:4, respectively, for 0 to 4, 5 to 9, 10 to 14, and 15 to 19 years before onset.

Trends in mortality from coronary heart disease and stroke among U.S. veterans; 1954-1979.

A cohort of nearly 300,000 insured veterans (Dorn Cohort), experienced a much greater percent decline in CHD death rate over the period, 1954-1979, than the population of the U.S., while for stroke, the percent decline in death rate was virtually the same as the U.S. For CHD, greater percent declines were noted over the study period for non-smokers compared to cigarette smokers, for professionals compared to non-professionals and for persons with high socioeconomic scores (SES) compared to those with low scores. In each group, younger persons experienced greater percent declines than older persons. For stroke, non-smokers experienced a somewhat greater percent decline in rate than smokers but this did not hold true for all age groups. Unlike CHD, professionals experienced a smaller percent decline in their stroke death rate than non-professionals, as did persons with high SES compared to those with low SES. The contradictory patterns observed for the two diseases with respect to occupation and SES suggest that the risk factors for stroke and coronary heart disease are not exactly the same. Throughout, the findings were much more convincing for CHD than for stroke.

Renal cancer and cigarette smoking in a 26-year followup of U.S. veterans.

The cigarette smoking habits of a cohort of almost 250,000 U. S. veterans were analyzed for their relationship to renal cancer. Information on smoking habits was collected in 1954 and in 1957 for nonrespondents to the first effort. Of the veterans, 84 percent returned their questionnaires. The cohort was followed for mortality until 1980, or 26 years. The followup of these military veterans, mostly of World War I, revealed 719 deaths from renal cancer, making this the largest study of renal cancer and cigarette smoking to date. Current smokers had a 47 percent increase in risk relative to nonsmokers. The relative risk for renal cancer increased significantly with the number of cigarettes smoked per day, from 1.31 for 1-9, 1.37 for 10-20, 1.60 for 21-39, and 2.06 for 40 or more. This analysis was unable to separate the risks of cigarette smoking for tumors of the renal parenchyma from those for tumors of the renal pelvis and ureter. However, the results suggest that almost one-fifth of all renal cancer deaths are attributable to cigarette smoking.

A comparative study on different methods of measuring Rn concentrations in homes.

Three methods of measuring 222Rn concentration in homes were compared. In 91 dwellings, measurements were made with thermoluminescence dosimeters (TLDs) for two weeks during the winter, with alpha track Track Etch type SF dosimeters (ATDs) for six months during the heating season and for one year. There was a high correlation between the TLD and the six-month ATD values (r = .83) and between the six-month and the one-year ATD values (r = .80). On the average, however, the arithmetic and geometric means of the ATD (six-month) values were approximately 50 Bq m-3 higher than the TLD values (p less than .0001). The six-month ATD values also were, on the average, approximately eight percent higher than the one-year values. This difference is probably caused by decreased ventilation during the colder part of the year. The results indicate that the measurement methods under study may be of value for exposure assessments in epidemiologic studies, but also that estimates of risk per unit radiation exposure should be interpreted with caution.

Mortality and career radiation doses for workers at a commercial nuclear power plant: feasibility study.

Career radiation doses for 8,961 male workers at the Calvert Cliffs Nuclear Power Plant (CCNPP) were determined for both utility (n = 4,960) and contractor (n = 4,001) employees. Workers were followed from the time of first employment at CCNPP (including plant construction) to the end of 1984 (mean follow-up = 5.4 y). Plant operation began in 1975. The mean duration of employment was 1.9 y at CCNPP and 3.1 y in the nuclear industry. Career radiation doses were determined from dosimetry records kept by the utility company and the U.S. Nuclear Regulatory Commission (NRC). For all exposed workers, the average career dose was 21 mSv and was higher for contractor (30 mSv) than utility (13 mSv) workers. Career doses were also higher among those employed in the nuclear industry for greater than or equal to 15 y (111 mSv) and among workers classified as health physicists (56 mSv). Cumulative doses of greater than or equal to 50 mSv were received by 12% of the workers; the maximum career dose reported was 470 mSv. The availability of social security numbers for practically all employees facilitated record-linkage methods to determine mortality; 161 deaths were identified. On average the workers experienced mortality from all causes that was 15% less than that of the general population of the U.S., probably due to healthier members of the population being selected for employment. Our investigation demonstrates that historical information is available from which career doses could be constructed and that, in principle, it is feasible to conduct epidemiologic studies of nuclear power plant workers in the U.S. Although difficult, the approach taken could prove useful until such time as a comprehensive registry of U.S. radiation workers is established.

Residential radon exposure and lung cancer in Swedish women.

A case-control study was undertaken to investigate the role of residential radon exposure for lung cancer. The study included 210 women with lung cancer diagnosed from 1983-1986 in the county of Stockholm and 191 hospital and 209 population controls. Interviews provided information on lifetime residences and smoking. Radon concentrations measured in 1,573 residences of the study subjects showed a lognormal distribution with arithmetic and geometric means of 127.7 and 96.0 Bq m-3, respectively. Lung cancer risks tended to increase with estimated radon exposure, reaching a relative risk of 1.7 (95% confidence interval: 1.0-2.9) in women having an average radon level exceeding 150 Bq m-3 (4 pCi L-1). Stronger associations were suggested in younger persons and risk estimates appeared to be within the same range as those projected for miners. However, further studies are needed to clarify the level of risk associated with exposure to residential radon.

Acute respiratory symptoms in patients with chronic obstructive pulmonary disease and in other subjects living near a coal-fired plant.

Daily symptom rates in patients with chronic obstructive pulmonary disease and in other subjects with presumed high sensitivity to air pollution who lived near a coal-fired plant were compared with 24-hr ambient air concentrations of nitrogen dioxide, sulfur dioxide, soot, and suspended particles as well as with emissions from the plant. The mean concentrations of each of the pollutants during the 4-month study period were below 30 micrograms/m3, and no single 24-hr concentration exceeded 100 micrograms/m3. There were no consistent associations between plant emissions and pollutant levels or between these two variables and daily symptom rates. The results indicate that the coal-fired plant was not of major importance for the occurrence of acute respiratory symptoms in the surrounding population.

Zygosity partitioning of small twin samples.

When the Weinberg estimate of the proportion of monozygotic pairs is quite deviant from that in the source population, it is likely to be wrong because Weinberg's difference is much less stable than the zygosity proportions. A formula is proposed for the probability distribution of possible compositions of a small sample of twins based on sex concordance in the sample and zygosity proportions in the source population.

The monozygotic twinning rate: is it really constant?

Weinberg's difference method, applied to twin birth statistics, usually shows a dependence of the MZ rate on maternal age, like a thin shadow of the DZ rate. Some of this MZ variation could be explained away by James' finding of more same-sex (SS) than opposite-sex (OS) DZ twins, the excess being mistakenly classified as MZ by Weinberg's assumption of equal numbers. By several methods one can extract a constant value for the MZ rate and a constant or nearly constant value for the DZ SS/OS ratio, but these "constants" are actually arbitrary and they vary between populations.

Trends in mortality from chronic obstructive pulmonary disease among U.S. veterans: 1954 to 1979.

Recent trends in chronic obstructive pulmonary disease (COPD) mortality are described for a cohort of nearly 300,000 insured veterans who were followed for survival from 1954 through 1979. Death rates from COPD for the veterans by smoking status were compared with U.S. death rates for white males 55 to 84 yr of age over the same period. The main findings were that the veterans experienced sharp increases in COPD mortality over the 26-yr study period, much like the U.S. findings. However, the observed increases were not as great as those for the United States. The COPD rates for veterans who were cigarette smokers showed the same pattern as for all veterans. Some important differences by age were noted. Thus, for ages 60 to 64 and 65 to 69, the direction of the trend among veterans appeared to change from initial increases in the COPD death rate to later decreases while at the same time the three oldest age groups (70-74, 75-79, and 80-84) continued to experience increases in mortality over the whole period. These findings were similar to those for the United States. Several possible explanatory factors for these changes are discussed.

Twin concordance. A more general model.

Estimation of the twin concordance rate for a disease often requires two stages. First, the disease is ascertained in a population or in a population sample, and such twins as are found with the disease become probands. Second, twin pairs with only one proband are further investigated and additional concordant pairs are thus discovered. A mathematical model is presented that allows for continuous variation in completeness of ascertainment in both stages, for correlation within pairs in the primary ascertainment process, and for correlation within pairs in occurrence of the disease. The concordance rate can be estimated by the proband method if secondary ascertainment is complete; other measures of concordance are accurate only if primary ascertainment is complete. A parameter analogous to the concordance rate but related to correlation in primary ascertainment can be estimated from the same data.